US 2012/0198973 discloses an indexable cutting insert configured for machining a metallic work piece by means of turning. The cutting insert includes an insert body having an upper side defining an upper extension plane, a lower side defining a lower extension plane parallel thereto, wherein a center axis extends perpendicularly through the upper extension plane and the lower extension plane. A clearance surface extends around the periphery of the insert body and connects the upper side and the lower side. A cutting edge is formed between the clearance surface and the upper side and extends around the upper side. The cutting edge forms a primary edge portion and a secondary edge portion connected by a nose edge portion such that the secondary edge portion is formed at an angle towards the primary edge portion. The upper side of the insert body includes a chip former with a nose bottom surface formed behind the nose edge portion along a bisector between the primary edge portion and the secondary edge portion. The nose bottom surface has a lowest point lower than the level of the nose edge portion. The chip former further includes a primary main bottom surface extending along the primary edge portion and having a lowest point lower than the level of the primary edge portion.
The cutting insert of US 2012/0198973 has a chip geometry in the corner area, including an elevated surface in the form of a step formed behind the nose bottom surface along the bisector. The elevated surface has a lowest point lower than the level of the primary edge portion but higher than the lowest point of each of the nose bottom surface and the primary main bottom surface. The elevated surface is formed symmetrically with respect to the bisector, such that part of the elevated surface is located in a region between the nose bottom surface and the primary main bottom surface, and part of the elevated surface is located between the nose bottom surface and a secondary main bottom surface extending along the secondary edge portion. Behind the elevated surface along the bisector, a further elevated chip geometry is formed. The cutting insert thus provides chip geometries at different levels in the region of the cutting corner.
The cutting insert of US 2012/0198973 thus provides chip control for different feed rates, wherein the different chip geometries are being used depending on feed rate. However, when used for chip-removing machining of a work piece by means of turning, the cutting insert gives hard chip forming, i.e. chips with a small radius of curvature are formed. This reduces the tool life due to the high deformation forces thus exerted.